46 C.F.R. § 28.545 – Intact stability when using lifting gear.

(a) Each vessel which lifts a weight over the side, or that uses fishing gear that can impose an overturning moment on the vessel, such as trawls and seines, must meet the requirements of this section if that maximum heeling moment exceeds 0.67(W)(GM)(F/B), in foot-long tons (meter-metric tons), where:
W = displacement of the vessel with the lifted weight or the force on the fishing gear included, in long tons (metric tons);
GM = metacentric height with the lifted weight or force on the fishing gear included, in feet (meters);
F = freeboard to the lowest weather deck, measured at amidships in feet (meters); and
B = maximum beam, in feet (meters).
(b) Except as provided in paragraph (f) of this section, each vessel must meet the requirements of § 28.570 or have at least 15 foot-degrees (0.080 meter-radians) of area under the righting arm curve, after correcting the righting arms for the heeling arm caused by lifting or fishing gear, from the angle of equilibrium to the least of the following:
1. (1) The angle corresponding to the maximum righting arm;
2. (2) The angle of downflooding; or
3. (3) 40° (0.7 radians).
(c) The angle of intersection of the heeling arm curve resulting from the lifting moment or the moment of fishing gear and the righting arm curve must not be at an angle of more than 10° (0.17 radians).
(d) The heeling arm curve resulting from lifting must be calculated as the resultant of the upright heeling moment divided by the vessel's displacement multiplied by the cosine of the angle of heel.
(e) For the purposes of this section, the weight of suspended loads must be assumed to act at the tip of the boom unless the suspended load's transverse movement is restricted, such as by the use of sideboards.
(f) A vessel that operates on protected waters, as defined in § 170.050 of this chapter, must comply with the requirements of this section, except that the area described in paragraph (b) of this section must be at least 10 foot-degrees (0.053 meter-radians).